The present invention relates to flush valves that control the flow of water from toilet tanks to toilet bowls. More particularly, the invention relates to a tank valve seat mountable to a toilet tank and preferably used with canister type flush valves.
Many systems for controlling the flow of toilet tank water to a toilet bowl are known. Such systems have a water inlet valve connected to the tank that is typically controlled by a float that reacts to the tank water level. Depressing a trip lever or other actuator moves a flush valve at the tank outlet so that water can empty from the tank into the bowl. As the tank water drains, an inlet valve float drops with the water level in the tank, thereby triggering inlet water flow to refill the tank. After sufficient tank water leaves the tank, the flush valve closes so that the water level in the tank can be re-established. As the tank refills after the outlet valve has closed, the supply valve float rises with the water and eventually closes the supply valve to shut off the water supply.
A variety of flush valves have been devised for controlling the flow of water from the tank to the bowl. One of the most common is the flapper type flush valve. Flapper flush valves have a pivotal yoke that supports a large diameter stopper that seals off the tank outlet until the trip lever is actuated to start a flush cycle. The large stopper is filled with air that slows the reseating of the stopper until sufficient water has been drained from the tank. On occasion, some such valves have difficulty in completely closing off outlet flow if the flapper doesn't drop onto the valve seat exactly right.
Another type of flush valve has a dedicated float that moves straight vertically upwards once tripped, and then straight vertically downward. See eg. U.S. Pat. Nos. 5,329,647, 5,896,593, 6,715,162, and 6,728,976.
A particularly preferred type of flush valve that works in this manner is the canister flush valve shown in U.S. patent application publication 2007/0101485, which is hereby incorporated by reference as if fully set forth herein. However, this type of canister design, when used with its shown valve seat, presents a number of design constraints.
For example, to achieve sufficient initial flow one may have to increase the diameter of the entry to the bowl's rear extension to a point where non-standard fittings are required, and/or aesthetics are affected. Moreover, the flow characteristics may be such as to limit certain water usage efficiencies that must be compensated for otherwise.
One complicating factor is that in order to insure vertical movement of the valve body, a guide is positioned on the valve seat. As this is typically at the center of the flow passage through the seat, the guide itself can impede flow and complicate design revisions. While U.S. Pat. No. 5,926,861 proposes to have the guide for the canister be at the periphery of the seat, it requires a relatively complex and expensive structure to implement that proposal.
In light of the above, improvements are needed to address these concerns.